苹果日烧病程中果皮抗氧化系统在细胞超微结构的变化

Changes in Antioxidative System and Cell Ultrastructure in the FruitPeels of Apple During Sunburn Development

以富士品种为试材研究了苹果果实日烧病程中果皮组织细胞膜脂过氧化、抗氧化酶类、酚类物质的变化规律,并用电镜观察细胞超微结构的变化。结果表明膜脂过氧化导致日烧发生并进一步使日烧程度加重。相应地,抗氧化酶类在果皮变白期活性激增,但是,细胞结构仍较完整,只是叶绿体膨胀、类囊体结构部分解体,线粒体周缘模糊,细胞质中含大量的空泡;以后果皮变褐,绿原酸、槲皮素、芦丁、杨梅酮积累,同时靠近上表皮几层细胞解体,由密集的电子致密物充塞,细胞壁加厚。

Fruits from 6-year-old apple trees(Malus domestica Borkh cv. Fuji) were used asmaterials to test the changes of antioxdative sys-tem and cell ultrastructrural of fruit peels duringsunburn development. Fruit sunburn appeared inmid July, 2002. The process of apple fruit sun-burn was divided into three phases (0:control):1: bleaching, 2: browness, and 3: necrosis. Fujiapple fruits in different sunburn state werepicked. Phenolic compounds, memberane pro-tective enzymes (SOD, POD, PPO, CAT), cellmemberane lipid peroxidation and cell ultrastruc-ture in fruit peel were studied. The result showedthat the degree of cell memberane lipidperoxidation enhanced along with developmentof sunburn(Fig.1). The activity of membraneprotective enzymes also increased remarkably(Fig.3). However, the cell structure kept itsintegrity, except some organelles which partlydisassembled, and cytoplasm and vacuoles be-came enriched with electron-dense substanceswhile fruit peels became pale (Fig.2-3). As peelbecame brown, chlorogenic acid, quercetin, ru-tin and myricetin accumulated (Fig. 4), and cellsof outer layers of the epidermis collapsedcorrespondingly, cell wall became thicker (Fig.2-6). It is suggested that changes in both cellultrastructrure and antioxidative system confirmthat physiological state of fruit peels becomesdisordered during sunburn development.